1. Technical Field
The present disclosure relates to an object detection apparatus and an object detection method that make it possible to, by using a result of a measurement made by a radar apparatus, accurately detect an object that is present in an area around the radar apparatus.
2. Description of the Related Art
In recent years, radar apparatuses have been installed aboard vehicles. Such an on-board radar apparatus detects an object that is present in an area around the vehicle, e.g. another vehicle, a pedestrian, a two-wheel vehicle, or an on-street installation. The on-board radar apparatus detects an object approaching from the front or side of the vehicle and measures the relative positions of the vehicle and the object or the relative velocities of the vehicle and the object. Then, in a case where the on-board radar apparatus has determined, according to a result of the measurement, that there is a possibility of a collision between the vehicle and the object, the on-board radar apparatus gives a warning to the driver or controls the running of the vehicle to avoid the collision.
Further, a system that monitors or manages road traffic by using a radar apparatus installed in an area around a road has been under development. For example, by using a radar apparatus installed in an area around an intersection, such a system detects a vehicle or a pedestrian crossing the intersection or measures traffic flow, thereby adaptively controlling a traffic light. Further, in a case where such a system has determined that there is a possibility of a collision between a vehicle and a pedestrian in a road, the system gives a warning to the driver to avoid the collision.
Further, radar apparatuses are installed, for example, to monitor airports or other facilities. Such a radar apparatus detects an object intruding from the sky or the ground and provides information to a related security system, thereby preventing the intrusion of the object.
Thus, radar apparatuses are used in various scenes to detect objects. A recent radar apparatus has such higher resolution as to be able to acquire radar measurement information on different places from the same object. For this purpose, the radar apparatus performs a grouping (also referred to as “clustering”) process on the radar measurement information belonging to the same object and determines an object region. It should be noted that the term “grouping process” means a process in which signals detected at certain intervals of observation are divided into groups and each of the groups (also referred to as “clusters”) is defined as an aggregate of signals reflected from a single object.
An example of such a radar apparatus is disclosed in Japanese Unexamined Patent Application Publication No. 2010-266225. Japanese Unexamined Patent Application Publication No. 2010-266225 discloses a technology for performing object detection by extracting a representative point of a local region from radar measurement information of the radar apparatus according to the distance from the radar apparatus, setting an object region range represented by a fixed shape (rectangle) and a direction (inclination) with the representative point as a reference point, choosing, as a member point, radar measurement information within the object region range that is close in reflection intensity to the representative point, and forming a group of the representative point and the associated member point.
However, the technology disclosed in the aforementioned Japanese Unexamined Patent Application Publication No. 2010-266225 determines, according to the reflection intensity, whether radar measurement information (candidates for a member point) within the object region range belongs to the same object as the representative point. This leads to wrong grouping in a case where the reflection intensity from an adjacent different object has been measured to the same extent as the reflection intensity of the representative point. For example, in a case where a pedestrian is located near a vehicle, the reflection intensities of the vehicle and the pedestrian may be measured with approximate values, depending on directions of reflection, although the reflection intensities of the vehicle and the pedestrian with respect to the radar apparatus are supposed to be different. This causes the vehicle and the pedestrian to be grouped into the same group, thus making it difficult for the radar apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2010-266225 to separately detect the pedestrian and the vehicle.